1. Technical Field
This invention relates to an information recording apparatus for recording a stream, an information reproducing apparatus, an information recording method and an information reproducing method. More particularly, it relates to an information recording apparatus, an information reproducing apparatus, an information recording method and an information reproducing method for appropriately supervising the information pertinent to a stream.
2. Background Art
Recently, proposal has been made for a variety of optical discs, such as DVR, as a disc-shaped information recording medium, amongst recording mediums that may be mounted to and dismounted from a recording and/or reproducing apparatus,. The optical disc as this recording medium has been proposed as a large-capacity medium having a capacity as large as several gigabyte. This optical disc is thought to be promising as a recording medium for recording AV (audio visual) signals, such as video signals.
Among the encoding systems for performing digital compression of AV signals, there is an MPEG2 (Moving Picture Experts Group 2) system. This MPEG2 is the format of compression of moving pictures of the international standard, aimed to achieve a high picture quality, with the aid of compression techniques such as prediction of motion compensation, DCT (discrete cosine transform), quantization and variable length coding. The MPEG2 is also applied for recording AV signals on a recording medium. For example, in recording analog video signals on a recording medium, video signals are encoded in accordance with the MPEG2 system, and an encoded bitstream is recorded on the medium. In TV broadcast of the digital system of recent origin, the AV stream, encoded with the MPEG2 system, is transmitted with a format called a transport stream (TS). In recording digital broadcast on a recording medium, such a system is used in which the transport stream is recorded in the state of digital signals, without decoding or encoding.
If the AV signals are recorded in a digital signal format, the AV signals may be copied on a different recording medium without deterioration. This poses a serious problem for the copyright owner of the AV signals. Thus, for restricting the copying of the AV signals, such a method is used in which the copy control information (CCI), as the copying restricting information, namely [copy free], [copy once], [no more copy] and [copy prohibited] is provided to the AV signals.
There is, for example, a CGMS (copy generation management system) signal for video signals. This CGMS is a system for controlling the number of times of possible copying on the part of the software. The CGMS for an analog interface is called CGMS-A, while that for a digital interface is called CGMS-D. The CGMS-A for analog is also called VBID because the ID is superimposed on the VBI (vertical blanking interval). This is standardized as EIAJ-CP-1204. If a reproducing apparatus is to analog-video-output non-copy-free AV signals, recorded on a recording medium, it is required that the CGMS shall be inserted in the video signals.
There is such a method in which a descriptor having the copy control information is encoded as the copy control information in recording a transport stream such as digital TV broadcast. Examples of this sort of the descriptor include DTCP (Digital Transmission Content Protection) provided for by DTLA (Digital Transmission Licensing Administrator) and a digital_copy_control_descriptor provided for by ARIB (Association of Radio Industries and Business) and used in BS digital broadcast of Japan. If the non-copy-free transport stream, recorded on a recording medium, is output by a reproducing apparatus in the state of the transport stream, it is required that this sort of the descriptor shall be encoded in the transport stream.
In recording the transport stream of for example the digital TV broadcast, there are two methods, namely a method in which a digital TV tuner enclosed in the recording apparatus is used as an input source, and a method in which an external set top box, called STB, is used as an input source. In the latter case, the STB and the recording apparatus are interconnected over an IEEE1394 digital bus. It is necessary in this case that the copy control information of the transport stream shall be guarded securely on the digital bus, in order to prevent the situation in which the copy control information is hacked on the digital bus such that its value is rewritten.
With this in mind, the aforementioned DTLA provides for a system in which the transport stream is transmitted using an IEEE1394 digital bus. This system is widely known as the so-called 5C system (DTCP-concordant system). In the DTCP system, the 2-bit information, called the Encryption Mode Indicator (EMI), is transmitted in a header of an isochronous packet, used in isochronous transfer of IEEE1394, this representing the encryption mode of the payload of the isochronous packet.
This EMI has, in association with the payload copy control information, the meaning of [00(=copy free)], [10(=copy once)], [01(no more copy)] and [11(=copy prohibited)]. In recording by the DTCP system, such a method is allowed in which the recording restriction is achieved using only EMI as the copy control information without analyzing the copy control information encoded in the transport stream (called Embedded CCI). This recording method is called the non-cognizant recording mode. On the other hand, the method which effects recording as the embedded CCI is analyzed is called the cognizant recording mode. The AV signals recorded on the recording medium in accordance with the DTCP system are required to be reproduced in accordance with the system conforming to the DTCP system.
Such a system is also studied in which the copy control information called the watermark is embedded in the baseband AV signals or in a MPEG bitstream. As for the watermark, activities for standardization are now going on and proposal has been made for a millennium system and a galaxy system. When the watermark has been formally introduced into the market, it is required that, when the MPEG bitstream or the AV signals, recorded on the recording medium, are reproduced by a reproducing apparatus, the watermark shall be embedded in the MPEG bitstream or the AV signals.
Turning to a recording apparatus for recording the MPEG bitstream on a recording medium, it may be premeditated that the input sources for recording will be variegated in time to come. For example,    (1) an MPEG stream obtained by the recording apparatus self-encoding the line input of analog video;    (2) an MPEG stream obtained by the recording apparatus self-encoding the video from a tuner input of the analog TV broadcast enclosed in the recording apparatus;    (3) a transport stream from a tuner input of digital TV broadcast enclosed in the recording apparatus;    (4) a transport stream input with the DTCP-concordant method over IEEE1394; and    (5) a transport stream input not with the DTCP-concordant method over IEEE1394 may be thought of as possible input sources.
For recording a transport stream of for example digital TV broadcast, there are two methods, namely a method in which the transport stream from the digital TV tuner enclosed in the recording apparatus is used as an input source, and a method in which the transport stream input from an external set top box (STB) via IEEE1394 is used as an input source. With the former method, the DTCP system need not be used, whereas, with the latter method, recording must be made using the DTCP-concordant method at least as long a the BS broadcast of Japan is concerned. Thus, in reproducing the stream recorded using the former method, there is no necessity of applying reproduction restrictions concordant with the DTCP system, whereas, in reproducing the stream recorded with the latter method, reproduction restrictions concordant with the DTCP system need to be applied.
Up to now, no information indicating [what is the input source of the transport stream recorded on the recording medium?] was recorded, so that appropriate reproduction restrictions could not be applied in reproducing the transport stream.
It is currently attempted to introduce the watermark into the DVD video, with a view to preventing the analog video output of the DVD video player from being recorded illicitly. On the other hand, the watermark is likely not to be introduced into the analog TV broadcast which basically may be recorded freely. In such situation, an input source of an MPEG stream, recorded on self-encoding the analog video line input, may possibly be a DVD video output, so that, when the MPEG stream is reproduced, it is required to check the watermark to apply reproduction restrictions. On the other hand, with the MPEG stream, recorded on self-encoding the analog TV broadcast, it may be premeditated that the watermark need not be checked at the time of reproducing the MPEG stream.
Heretofore, [what is the input source of the MPEG stream recorded on the recording medium?] was not recorded, such that appropriate reproduction restrictions could not be applied in reproducing the corresponding MPEG stream.
On the other hand, in recording the transport stream in accordance with the DTCP-concordant system, either the cognizant recording mode or the non-cognizant recording mode may be used. When the transport stream, recorded by the cognizant recording mode, is decoded to reproduce the analog video, it is unnecessary to check the watermark or the Embedded CCI of the transport stream. However, when the transport stream, recorded by the non-cognizant recording mode, is decoded to reproduce the analog video, it is necessary to check the watermark or the Embedded CCI of the transport stream.
Heretofore, the information indicating [Which is the recording mode of the transport stream recorded on the recording medium, the cognizant recording mode or the non-cognizant recording mode?] was not recorded, so that, when the transport stream is reproduced, it was not possible to verify whether or not the check of the Embedded CCI or the watermark was necessary.
Moreover, if the watermark was checked in recording an AV stream, it is unnecessary to check the watermark in reproducing the AV stream. If conversely the watermark was not checked in recording an AV stream, the watermark needs to be checked in reproducing the AV stream.
Up to now, the information indicating: [Was the watermark checked at the time of recording the AV stream currently recorded on the recording medium?] was not recorded, so that it could not be verified whether or not the watermark needs to be checked at the time of reproducing the transport stream.